[Moldmaker]

For the past 2 years I have read several threads about the implied shortcomings of the battery and charging system. It seems that whenever there is an issue of a battery going flat or the addition of load to the electrical system, one of the common replies is to “ride the bike for a while with the engine revving above 5000 rpm because it doesn’t start charging until this speed”. I have to assume that this is based on the alternator specification in the service manual: 14 V/310 W at 5,000 r/min. I had my doubts as to whether this was an accurate statement, and decided to measure the output.

First of all, it should be noted that the FZ6 has a standard 3-phase alternator with NO rotor current control circuitry. In other words, it will generate voltage across the output terminals as soon as it begins rotating, increasing with speed, as it uses permanent magnets in the rotor. In addition, the regulator/rectifier module is an external package, mounted just below and to the left of the rear fuel tank mount. This allowed for easy access to make measurements.

I began by leaving the lights and 4-way flasher on for about ½ hour to create some drain on the battery as I have the dual headlight mod. Voltage dropped from 12.2 V to 11.0 V. After splicing in a shunt between the positive terminal of the regulator and the lead going towards the rest of the system I started the engine. The attached chart shows a graphical display of the measured values listed here:

Engine off- 11.25V
Started from cold fast idle- 12.8V, 20A, 1600 RPM
High beam and emergency flasher on- 12.2V, 20A, 1500 RPM
Warmed up, low beam, emergency flasher off- 12.2V, 15A, 1100 RPM
Warmed up- 13.8V, 21A, 2000 RPM
Warmed up- 14.0V, 22A, 2200 RPM
Warmed up- 14.0V, 22A, 4000 RPM
Warmed up- 14.0V, 22A, 5000 RPM
Warmed up- 14.0V, 22A, 8000 RPM

After gathering this info, I hooked up an additional ammeter at the main fuse block to monitor system usage. Following the same approach as before, I measured both positive and negative current flow consistent with the rpm points listed above. The point of no charge was about 1400 RPM, with battery drain below this speed and charging current above. The maximum positive charging current measured was 4A @ >2000 RPM, as the regulator was showing an output of 22A. I didn’t let this run for more than 5 minutes so I never reached a point where the battery would reach a full charge state.

My data leads me to the following conclusions:
1- The alternator/regulator package produces it’s full rated value of 310W (22A x 14V) at 2200 RPM and this value never increases with engine speeds above this point. So, the advice to “keep it revved up or it will never charge” is misguided. Just normal engine speeds are enough to get full charging potential.
2- As I stated, I have the dual headlight mod. With this, my bike draws a consistent 18 amps under steady operation. Of course, as brakes are applied or turn signals are activated, this load momentarily increases above 18A to a discharge condition. I am confidant that the normal total electrical draw is just under the system limits, which is why I haven’t had a problem with a battery discharging. I did have a regulator fail when the bike was under warranty, but no problems since.
3- The numbers don’t lie: I don’t believe that this electrical system can handle more that an additional 40-45W of constant current draw without eventually discharging the battery. Momentary use is one thing but with a battery capacity of only 10 A/H there is very little headroom. The effects of this can be masked/minimized by hooking the battery up to a charger on a regular basis, but you will not be able to maintain charge by running the engine unless:

total system demand<charging potential
??? amps<22 amps

I hope this is helpful to some of you as I spent some time debating whether or not to get involved in the discussion. Comments or questions, just fire away..